Research On Mechanism And Application Of Mass Concrete Temperature Crack Control

The problem of mass concrete temperature crack has been one of importantsubjects which are concerned for a long time and needed to be solved urgently in theengineering. Based on predecessors’ works, the mass concrete temperature crackcontrol theory and method of application were deeply researched from the twoperspectives of theoretical and application in this paper. The main contents are asfollows:(1)The mechanism of mass concrete temperature cracks was mainly studied fromthe following aspects: firstly key factors of mass concrete cracks control was analyzed;secondly the thermal stress and constrained deformation was studied, the thermal stresscalculation formulae of mass concrete structure under inner or outer constraint andexpounded the effect of constraint on creep relaxation and elastic modulus wassummarized; finally, the relationship of stress increment and strain increment undersingle stress action was established by analyzing creep stress of mass concretestructure.(2)For limitations of current code for construction of mass concrete(GB50496-2009) in some respects, it was put forward that during mass concrete mixratio optimal design, a proportion of emulsified asphalt mixture was mixed into massconcrete as concrete admixture, material optimum and mix optimization of a new typecompound mixed with emulsified asphalt, fly ash and chemical fiber were conducted.Some mechanical properties tests, cube compressive axis, compressive, splitting tensile,the static pressure elastic modulus, axial tensile of the new type compound of massconcrete were researched, then, some valuable experiment results and suggestions were gotten.(3)According to the theory of “resist and release”, the “resist and release”elastic-sliding model was established, its mechanical analysis and calculation wasconducted. As the study on the mass concrete construction cracks control problemsabout application of elastic-sliding model in many deep mine shaft lining existed someblank appearance, the hydration exothermic reaction, temperature regime andtemperature stress of high performance concrete of the deep frozen shaft lining wasanalyzed, the temperature field mathematical model of high performance concrete shaftlining was constructed, the basic differential equation of deformation of highperformance concrete shaft lining was established and the new technology of highperformance concrete shaft lining cracks control into engineering practice was applied,which got better social benefits and economic benefits.(4)The temperature field of mass concrete is unstable (temperature field). As thesize of placing layer direction of mass concrete is far less than the size of horizontaldirection, and heat transfers only in thickness direction, the method to calculate massconcrete is suitable for difference method. Through the study of heat exchange theoryof mass concrete and the boundary conditions of heat transfer equation, the model offinite difference method of mass concrete one-dimensional temperature field wasestablished and the calculation of one-dimensional temperature field with concreteengineering practice was conducted.(5)According to the existing problems of the condenser tube used in thetraditional mass concrete temperature crack control, combined with the theory of“resist and release” and the characteristics of aluminum plastic pipe, a systematicstudy on key technology about the application of aluminum plastic pipe in massconcrete was conducted, such as design requirement of aluminum plastic pipe ascooling water piping, establishment of the concrete theological model with aluminumplastic pipe as condenser tube, the relationship of stress and strain of aluminum plasticpipe and analysis and calculation of the anti-floating problem of aluminum plastic pipein construction under thermal stress action.(6) The limitations of deformation joint in mass concrete temperature crackcontrol were analyzed, and it was pointed out that setting aluminum plastic pipe as internal deformation pipeline can take the dual function of controlling temperaturecracks and ensure mass concrete structural integrity. Aiming that pre-buried aluminumplastic pipe in mass concrete may lead to problem of section weaken, the equivalentsecond moment of area and equivalent width of mass concrete in the vertical directionof aluminum plastic pipe and along direction of aluminum plastic pipe were calculated,then the deformation of flexible release seam of aluminum plastic pipe was analyzed,the absorbed strain energy of aluminum plastic pipe by deformation was calculated, theproblem of deformation energy dissipation between aluminum plastic pipe and massconcrete was studied and some conclusions and suggestions for reference were gotten.